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Analysis of changes of cloudiness in Poland

Analysis of spatial and physical changes of cloudiness in Poland over the years 1988-2013 from the perspective of solar energy potential performed on a basis of the AVHRR satellite data.

Project leader: Dr. Jan Musial
Duration: 22.08.2014 – 21.08.2017

Research project objectives

The main objective of this project is a spatio-temporal analysis of changes in cloud cover distribution and its physical properties in Poland over the last 25 years. The secondary objective is an impact assessment of those changes on solar energy potential. Analyses will be performed on the basis of satellite data acquired by the Advanced Very High Resolution Radiometer (AVHRR) at the resolution of 1 km2. Results of this study will verify the hypothesis, that changes of local climate related to anthropogenic factors such as: run-down of heavy industry or expansion of urban areas, are reflected in cloudiness characteristics and solar irradiation.

Research methodology

The research methodology will be divided in 3 steps. At the first stage, the extensive AVHRR data archive collected by the University of Bern (Husler et al., 2011) will be employed to generate satellite Climate Data Records (CDRs) with the following cloud cover characteristics: top and base altitude, optical depth, droplet effective radius, cloud phase, and liquid/ice water path. Cloud detection on satellite imagery will be performed by means of the PCM algorithm (Musial et al., 2013), whereas the cloud physical properties will be derived by the PPS package (Dybbroe et al., 2005; Roebeling et al., 2006). Special emphasis will be put on data homogeneity, originating from several generations of the AVHRR instrument by utilising suitable calibrations coefficients (Heidinger et al., 2010) and by employing diurnal cloudiness cycle correction (Foster and Heidinger, 2013). In order to verify the applicability of the acquired CDR to climatic analyses, their monthly mean values will be validated against Moderate Resolution Imaging Spectroradiometer (MODIS) cloud products.

Second phase of the project will embrace computation of the 25-yr solar irradiation time series by means of the r:sun model (Suri and Hofierka, 2004). This will involve derivation of the clearness index kt, defined as: kt = G/Gclear (Hammer et al., 2003), where Gclear indicates solar irradiance for clear-sky conditions and G indicated the same quantity for overcasted sky. Both quantities will be computed from the libRadtran RTM simulations (Mayer and Kylling, 2005), which will associate cloud characteristics with the atmospheric transmittance. Simulated cloud radiative forcing, expressed by day to day variations of solar irradiation, will be validated against analogues data retrieved from ground measurements.

The last part of the project will consist of spatio-temporal analysis of the acquired 25-yr CDRs containing cloud cover characteristics and solar irradiation. Acquired inconsistencies in time series and climatic trends will be correlated in time with local anthropogenic factors. On this basis conclusions about possible changes of local climates in Poland will be drawn.

Research project impact

The main outcome of this project will consist of quantitative maps containing cloud cover characteristics change in Poland over the last 25 years, together with associated variations of solar irradiation. The acquired 25-yr CDRs at the resolution of 1 km2 will be significantly more accurate than estimates interpolated from a sparse network of ground meteorological stations, or from other available satellite data sets (Karlsson et al., 2013). This will allow detections of climate trends and anomalies in cloud cover characteristics and solar irradiation induced by the local anthropogenic factors such as: run-down of heavy industry, reduction of fossil fuel combustion, implementation of clean technologies or expansion of urban areas. Performed analyses will allow to quantitatively assess the cloud radiative forcing as a day to day solar irradiation variation expressed in Wh/m2. The practical aspect of the acquired results will be related to support of solar investments in Poland by discriminating regions where there are becoming more profitable. Finally the developed CDRs will contribute to future climate analyses.

                                                                    Credits by: NASA, CERES Team